Introduction to Helminths

00:01 Hello, and welcome to Parasites: Helminths. We are going to take a deeper look into some helminthes that cause human infections. And after you listen to this lecture, you will understand the lifecycles of helminths such as ascaris, hookworm, trichinella and schistosomes and how they are transmitted to humans. You will be familiar with the pathogenesis of the different forms of helminth infections, and you will know how to prevent and treat infections with helminths.

00:35 So again these are worms, these are multicellular animals or metazoa. We've been talking about protozoan parasites, single celled parasites, now we move to multicellular parasites, metazoa.

00:52 And the helminths are worms, are divided into two general categories; we have the roundworms, also known as nematodes or non-segmented roundworms, and then we have flatworms, these are asymmetric in cross section. Roundworms and flatworms. Worms reproduce sexually; there are male and female worms that mate to produce offspring. Again we're talking about worms in general; we're talking about roundworms, nematodes, non-segmented roundworms. An example of this is shown right here. In this photograph, ascaris lumbricoides, that's a typical worm we'll talk about and then we'll talk about the hookworms, another kind of nematode or non-segmented roundworm. Helminths can also be divided into flatworms as I said, these are asymmetric in cross-sectioned, a photograph of such a flatworm is shown here. These are segmented flatworms, or cestodes or tapeworms, again so the flatworms can be further divided. These can be millimeters to meters in length and there are non-segmented flatworms also called trematodes or flukes. These are typically short, with non-segmented bodies and we will talk about an example of this as well and that would be schistosoma.

02:28 Alright, back to roundworms. Again helminths, nematodes are roundworms, the example is ascaris